Chapter 1 Tro Notes- Matter, Measurement, and Problem Solving (1)

Chapter 1: Matter, Measurement, & Problem Solving

A. What is Chemistry?

• Chemistry is the science that deals with matter and the changes it undergoes.

• Known as the "Central Science" due to its connection to many natural phenomena.

B. Scientific Problem Solving

1. **Steps: **

   • State the Problem & Make Observations:

     • Observations can be:

       • Quantitative: Involving numbers/measurements.

       • Qualitative: Not involving numbers.

   • Formulate a Hypothesis: A potential solution.

   • Perform Experiments:

     • Test the hypothesis.

     • Results may lead to modifying the hypothesis and further experiments.

   • Form a Conclusion: Based on claim, evidence, reasoning.

2. Theory vs. Law:

   • A theory is a well-accepted explanation that can evolve with new evidence.

   • A law describes observed behaviors (e.g., Law of Conservation of Mass).

C. States of Matter

• Matter: anything that has mass and volume.

• Characteristics of the Three States:

  • Solids:

    • Definite shape and volume.

    • Particles packed tightly and vibrate gently.

  • Liquids:

    • No definite shape; takes the shape of the container.

    • Definite volume and particles can move freely.

  • Gases:

    • No definite shape or volume, spread to fill the container.

D. Physical and Chemical Properties and Changes

• Physical Properties: Color, odor, density, hardness, solubility, melting/boiling points.

• Chemical Properties: Reactions with acids/bases, oxidation, etc.

• Changes:

  • Physical Change: Alters physical state without changing chemical composition (e.g., melting, boiling).

  • Chemical Change: Involves rearranging atoms to form new substances (e.g., color change, heat production).

E. Elements, Mixtures, and Compounds

• Element: Cannot be broken down by chemical means (118 known elements).

• Compound: Formed by bonding elements with a fixed composition (e.g., H2O).

• Mixture: Varying composition of pure substances.

  1. Homogeneous: Uniform composition (e.g., saltwater).

  2. Heterogeneous: Distinct regions (e.g., chocolate chip cookie).

F. Energy

• Energy is defined as the ability to do work (move something).

• Types of Energy:

  • Potential: Stored energy (e.g., elastic, gravitational).

  • Kinetic: Energy of motion (e.g., thermal, electrical).

• Energy is conserved, and lower energy states are more stable.

G. Measurement

1. Quantitative Properties: Allow determination of properties like mass and density.

2. Scientific Notation:

   • Used for large/small numbers.

   • Format: A number between 1 and 10 x 10^n.

   • Example: 42000.0 = 4.2 x 10^4

3. Units of Measurement:

   • Basic SI Units:

     • Mass (kg), Distance (m), Time (s), Temperature (K).

   • Unit Conversions: Use conversion factors and dimensional analysis to convert units.

H. Derived Units and Density

• Volume: Common units are Liters (L) and milliliters (mL).

• Density Formula: Density = Mass/Volume.

I. Uncertainty, Significant Figures, and Rounding Off

• Uncertainty exists in measurements due to equipment limitations.

• Significant Figures: Digits that provide meaningful information.

  • Rules:

    1. Exact numbers have unlimited significant figures.

    2. In multiplication/division, limit to the least significant figures.

    3. In addition/subtraction, limit to the least decimal places.

• Rounding Guidelines:

  • Digit < 5: round down.

  • Digit > 5: round up.

  • Exact number 5: round to nearest even if ambiguous (known as "perfect 5").